Tire anatomy and construction

Anatomy of a tire

Get an inside look at each of the elements that make up a typical tire.

1. Airtight synthetic rubber liner

Most modern tubeless tires are constructed with a virtually impermeable butyl rubber liner. This liner replaces the old inner tubes. Check your tires' air pressure monthly, as some air loss occurs over time.

2. Carcass ply

The carcass ply is comprised of thin textile fiber cables that are bonded into the rubber. These fiber cables are largely responsible for determining the strength of the tire.

3. Beads

The beads are responsible for clamping the tire firmly against the rim of the wheel.

4. Sidewall

In addition to giving the tire its height, the sidewall protects the tire against impacts with curbs and other objects. The sidewall also contains all the markings which tell you the important information about the tire, such as speed rating, load rating, and tire dimensions.

5. Crown Plies

Crown plies provide the rigid base for the tread which allows for good gas mileage. The plies also provide centrifugal and lateral rigidity to the tire, while also allowing the tire to flex sufficiently for a comfortable ride.

6. Tread

The tread is designed to provide traction in a variety of conditions. Good tread design also resists wear, abrasion, and heat. On the sidewall, you can find branding that identifies the materials and number of layers of each of the different types of materials used to construct the tire. For example, a typical tire might have the following basic construction material listed:

Tread 2 Polyester + 2 Steel + 1 Nylon Sidewall 2 Polyester

In the example above, the "TREAD 2 POLYESTER" indicates that there are two radial body plies of polyester cord molded into the rubber under the centerline of the tread. In addition, the "2 STEEL + 1 NYLON" indicates that there are two belts of angled steel cord and one ply of circumferential cap nylon cord. The "SIDEWALL 2 POLYESTER" indicates that the tire has two radial body plies of polyester cord in each sidewall at the widest points of the tire's section width. (The section width is the distance between the tires inner and outer sidewalls). The two polyester sidewall plies are a continuation of the same two polyester body plies under the tread's centerline.

Many high-speed tires are constructed with additional reinforcements above the steel belts. Typically, these circumferential reinforcements can take the form of full cap plies and/or belt edge strips. Full cap plies are additional plies that cover the entire width of the steel belts. Belt edge strips are bands (approximately 1 inch wide) that cover only the inner and outer edges of the steel belts. Belt edge strips will not be listed in the materials branding for the tread area because they do not reside under the centerline of the tread, but at the inner and outer edges of the steel bands.

Similar to high-performance tires, many ultra-high performance tires are constructed with additional reinforcement to their sidewalls. Typically, fabric or steel cord is used in the sidewall construction to increase cornering stability and steering response. Just as the belt edge strips are not listed in the materials branding for the tread area because they do not reside under the centerline of the tread, sidewall reinforcing material is not generally listed in the materials branding for the sidewall area because the material is not present at the widest points of the tire's sidewall.